Resonance Raman studies of visual pigments and bacteriorhodopsin.
Item
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Title
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Resonance Raman studies of visual pigments and bacteriorhodopsin.
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Identifier
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AAI8801705
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identifier
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8801705
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Creator
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Deng, Hua.
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Contributor
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Adviser: R. H. Callender
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Date
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1987
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biophysics, General
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Abstract
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We have obtained the resonance Raman spectra of bovine rhodopsin, bathorhodopsin, and isorhodopsin for a series of isotopically labeled retinal chromophores. The specific substitutions are at retinal's protonated Schiff base moity and include HC=NH{dollar}\sp+{dollar}, HC=ND{dollar}\sp+{dollar}, H{dollar}\sp{13}{dollar}C=NH{dollar}\sp+{dollar}, and H{dollar}\sp{13}{dollar}C=ND{dollar}\sp+{dollar}. Apart from the doubly labeled retinal, we find that the protonated Schiff base frequency is the same, within experimental error, for rhodopsin and bathorhodopsin for all the substitutions measured here and elsewhere. We develop a force field which accurately fits the observed ethylenic (C=C) and protonated Schiff base stretching frequencies of rhodopsin and labeled derivatives. Using MINDO/3 quantum mechanical procedures, we find that the Schiff base frequency should be measureably affected by a 3.0 to 4.5 angstroms movement of a negatively charged counter-ion from the positively charged protonated Schiff base moiety. That there is no experimentally discernible difference in the Schiff base frequency between rhodopsin and bathorhodopsin suggests that models for the efficient conversion of light to chemical energy in the rhodopsin to bathorhodopsin photoconversion based soly on salt bridge separation of the protonated Schiff base and its counter-ion, are incorrect.;We have also studied the 'Schiff base mode' in doubly labeled (H{dollar}\sp{13}{dollar}C=ND+) retinal chromophore in rhodopsin and bathorhodopsin in more detail. In both resonance Raman and FTIR difference spectra, the 'Schiff base mode' has different band positions in rhodopsin and bathorhodopsin, however, the two kinds of spectra suggest just the opposite assignments for this mode. We have carried out Raman and IR intensity calculations to show that both rhodopsin and bathorhodopsin have these two modes which give opposite intensity patterns in Raman and IR spectra.;We have also studied bacteriorhodopsin, which is in many ways similar to rhodopsin. The works on bacteriorhodopsin include: (1) the proton-deuteron exchange time in bacteriorhodopsin under various conditions. (2) deionized form of bacteriorhodopsin. (3) The effort to obtain spectrally distinguishable M412 intermediate from bacteriorhodopsin has been unsuccessful.;Finally, we have probed the possibility to use SERS to study bacteriorhodopsin. We have shown that in our experiments, the electromagnetic effect in theoretical formulation of SERS is the main factor.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
